The present invention relates generally to a multiple solenoid-actuated control valve for a vehicle anti-lock brake system and, in particular, to a removable module attached to the valve which includes solenoid coils for actuating the valve.
Anti-lock brake systems are becoming increasingly popular with vehicle operators. Such systems provide precise control of brake applications under adverse operating conditions such as rain, snow or ice and during panic stops. An anti-lock brake system typically includes a control valve which is incorporated in the brake hydraulic circuit for modulating the hydraulic pressure applied to the brake cylinders. Anti-lock brake systems further include an electronic controller which actuates the solenoid valves. The electronic controller is responsive to vehicle operating parameter signals from various sensors located on the vehicle.
The control valve has a plurality of solenoid activated valves which control the hydraulic pressure applied to the individual brake cylinders. Typically, the solenoid valves are installed as a unit, with each solenoid valve armature, coil and electrical connector assembled therein. One example of a prior art control valve wherein the solenoid coils are separable from the valve armatures is illustrated in FIG. 1 at 10. The control valve 10 has a valve body 11 which is connected to other hydraulic components of the anti-lock brake system (not shown) to form a hydraulic circuit. An example of an anti-lock brake system which can utilize the valve body shown in FIG. 1 is described in U.S. Pat. No. 4,865,399. The valve body 11 includes a plurality of solenoid actuated valves (not shown) for controlling the flow of brake fluid within the anti-lock brake system. The control valve 10 has both solid and hollow armature solenoid valves. The hollow armatures include axial passages for the flow of brake fluid. Depending upon the type of armature, the solenoid valves have closed end armature casings 12 or open end armature casings 13 extending from the valve body. As will be explained below, the open end armature casings 13 allow flow of hydraulic fluid through the hollow armatures.
The solenoid valves are actuated by solenoid coils 14 disposed about the extended armatures 12 and 13. Each coil 14 has a pair of lead wires (not shown). The individual coils 14 are covered by metal coil casings 15 which complete the magnetic circuit for the solenoid. The coils 14 and coil casings 15 are mounted upon a plastic lead frame 16. The lead frame 16 is attached to an end of the valve body 11 by a plurality of manifolds 17 which are secured to the valve body 11 by threaded fasteners 18. The manifolds 17 have internal passages to return the brake fluid passing through the hollow armatures and open end armature casings 13 to the valve body 11. The control valve 10 has a first resilent gasket 19 forming a seal between the lead frame 16 and the valve body 11.
The lead frame 16 is molded about a printed circuit board (not shown) to which the coil lead wires are electrically connected. The printed circuit board connects the coil leads to individual pins 20 carried by a multi-pin connector 21 formed on the lead frame 16.
The control valve 10 includes a second resilent gasket 22 covering the top of the lead frame 16. The second resilent gasket 22 has a plurality of apertures 23 formed therethrough which receive the pins 20 of the multipin connector 21. A cover 24 is attached to the valve body 11 by extended threaded fasteners 25. The cover 24 houses a circuit board (not shown) which carries the female element of the multipin connector (not shown). The female element receives the pins 20 of the multi-pin connector 21. The circuit board housed by the cover 24 typically includes electronic circuitry for controlling (not shown) the anti-lock brake system. The cover 24 also carries an external electrical connector 26 for connecting the control valve 10 to other electrical components (not shown) of the anti-lock brake system. Thus, the second gasket 22 provides a seal to protect sensitive electrical components from leaking brake fluid and other contaminants present in the surrounding environment.
For the prior art valve shown in FIG. 1, the solenoid coils 14 could be contaminated by brake fluid leaking from the manifolds 17 since the manifolds 17 are located in the portion of the valve containing the coils 14. In addition, if the second gasket 22 does not form an adequate seal, leaking brake fluid could reach the electronics located between the coil lead wires and the external connector 26. An improperly sealed gasket could allow contamination of the electronics by the outside environment.
Servicing the solenoid coils 14 requires removal of the lead frame 16. Removal of the lead frame 16 requires opening the hydraulic circuit since the manifolds 17 must be removed first. Invariably, opening the hydraulic circuit introduces air into the hydraulic lines which must be bled upon reassembly. Furthermore, the multi-pin connector 21 must be disconnected for removal of the lead frame 16. System reliability is adversely affected if a good electrical connection is not made upon reassembly of the multi-pin connector 21. Thus, inclusion of the solenoid coils 14 within the valve body 11 is complex, requiring many parts.